Rock music is a kind of music (music genres) that began to be popular in the mid 50s. Its root was derived from rhythm and blues, country music from the 40s and 50s as well as the other various influences. Furthermore, It also took a variety of other musical styles, including folk music (folk music), jazz and classic music.
The distinctive sound of this music often revolved around the electric guitar or acoustic guitar, and the use of a very subtle back beat in the rhythm section on electric bass guitar and drums, and keyboards like organ, piano or synthesizers since the 70s. Besides the guitar or keyboard, saxophone and blues-style harmonica were sometimes used as a solo instrument. In its pure form, the rock music had three chords, a consistent and striking back-beat, and attractive melody.
In the late 60s and early 70s, it evolved into several types. Rock music that mixed with the folk music (local music in the US) became folk rock, the music that mixed with blues became blues-rock and the one that mixed with jazz became a jazz-rock fusion.
In the 70s, rock combined the influence of soul, funk, and Latin music. Also in 70s, rock evolved into various sub-genres (sub-categories), such as soft rock, glam rock, heavy metal, hard rock, progressive rock, and punk rock. The sub-categories of rock that were popular in the 80s were the New Wave, a hardcore punk, and alternative rock. In the 90s, there was grunge, Britpop, indie rock and nu metal.
A group of musicians who specialize in playing this music is called rock band or rock group. Many rock groups consist of guitar player, lead singer, bass guitar player, and drummer. In this case, they form a quartet.
Some rock groups take one or two positions above or use the main singer as a music player in addition to singing. In this case, they form a duo or trio. Another group has additional musicians like two rhythm guitars or a keyboardist. Somewhat less frequently, the rock group uses stringed musical instruments such as violin, cello or blower, such as saxophones, trumpet or trombones.